5 Gbps Optical Wireless Communication using Commercial SPAD Array Receivers

Photon counting detectors such as single-photon avalanche diode (SPAD) arrays can be utilized to improve the sensitivity of optical wireless communication (OWC) systems. However, the achievable data rate of SPAD-based OWC systems is strongly limited by the nonlinearity induced by SPAD dead time. In this work, the performances of SPAD receivers for two different modulation schemes, namely, on-off keying (OOK) and orthogonal frequency division multiplexing (OFDM), are compared demonstrating contrasting optimal regimes of operation. We employ nonlinear equalization and peak-to-average power ratio optimization by adjusting the OFDM clipping level to achieve record experimental data rates of up to 5 Gbps. In particular, the experimental results demonstrate the achievable data rates of 3.22 Gbps and 5 Gbps when OOK and OFDM are employed, respectively. It is also illustrated that to achieve the best data rate performance over a wide range of received power, adaptive switching between OOK and OFDM may be utilized.